Half-tone screen.



J. A. H. HATT. HALF TUNE SCREEN. APPLICATION FILED 11.24, 1911.

Patented July 8, 1913.

2 SHEETS-SHEET 1.

ITED -iiIos'Ei HAivri uR H iiRY nA'r'r, OF NEW sass; N. Y.

'nAtrronn SCREEN To ditto/2pm; ;z 12 mcgkconcem own that I, Josnrri-,An'rnun H. r enofi;- the United States, residing.in .tlie;borougl1 of Brooklyn, in the city j and State;of ,lTewr.Yorl have invented new and .useful Improvements in. Ha-lf-Tone Screens,ofwhichlthe following is a specification.

I his inventioni relates to'vscreens or gratings for useg' n producmg photo-mechan1cal printing platgasofillustrations; and more particularly. in -.certain aspects thereof; the invention relates .to screens for use in the camera for making halftone negatives, from which; printing .,plates are made photomechanically;

The objects of -Lthe invention will in part be set forth hereinafter and in part will be obvious to those skilled in the art.

-;The invention consists in the novel parts,

-articles, arrangements, combinations and improvements; herein shown and described.

' w-The ;aecompanying drawings, which are referred to herein v and constitute a partltereof, illustrate-a screen constructed in accordancejjvith vthe principles of the inventron:-

{.Of Figure 1 illustrates one ofthelplates Qf flV hlC-l l the screen is made; Fig. .2; illustratesflthe other plat-e constituting thescr'eenpliig. 3 shows the plates put together;withthe, air gap between; Fig. 4 ushows; the effect. through the two plates by i .transmitted light;:Figj5 shows one plate for; making a screenwlth a different kind of r ruling;; F i g..6 shows the other plate constitutin the screen Fi 7 shows them mountg U 7 g 1 ed w th ;an air gap between; and Fig. 8 is looking through the two superimposed plates by transmitted light.

In reproducing pictures with printing plates by thehal ftone process, the great d'e sideratumis tossecure the perfect rendition of all of the-gradations of the original in thereproduction; in other words to secure a full value for all the infinite combinations of lights and'shades from one extreme to the other in order that the impressionsmade Specification of Letters Patent.

".1 Patented July 8,191

inaret h s t t mi 1 fser 'iaimileoisao. '1

treme highlights as well as the detail: in the deepest darks, together with the .true' value of the middle tones.

One of the practical diflicu'lties has been that any effort directed toward preserving the gradationsin the. highlights has resulted in losing the detail in the darks; and-onthe other hand efforts to preserve the detail or modeling in the darks have done this at the expense of the highlights and middle tones.

The screen of the present invention retains in a remarkable and unusual degree both the highlights andv the deep shadows, while at the same time it brings out the middle tones or intermediate grays to an'unusual degree.

One reason for the difi'iculty in producing a correct range of gradations with the ordinary screens now in use is that they, or rather their component parts, are cemented together with a transparent balsam .which has the property of making the two -piecesor parts of the screen act to therays' oflight practically as one homogeneous mass of glass,'in other words a ray of light passing through the small interstices of the screen is not deflected or diffused, Such screens have the property of allowing the pencils of'light to be too nearly parallelor to emerge from the screen opening in too straight a line. My invention corrects this defect. to a great degree, by giving the ray of light a slight diffusion when it strikes the gap or air space between the glasses comprising the screen, and then again when it strikes the other glass after leaving the gap or air space. Practical testsinthe camera have shown that this air space in the screen of my invention, as distinguished from the present make of, screens does ena able. the production of a superior quality of negative as regards the gradations and'enables a superior negative to bemade with less effort. 1

. 1 I While with the screens heretofore in use, to make zr-,nega-' there is usually a tendency tive with What is known as a screeny f.,ef feet, that 1s, where the screen is too evident in the resulting negativebecause the action of the screen not elastic enough linallow ing the pencils of light to reproduce the.

varyingrgradationsof the origrnali'i the pensaid rulings are spaces 3 of relatively greattranslucency and thesemay be'in whole or part of the glass only. In Fig. 2 of the drawings is shown a plate t. Said plate has rulings 5 thereon, which rulings also may be to some degree translucent. Between said rulings are the spaces 6 which are also of greater translucency than the rulings 5 and=preferably are'the clear glass. These rulings 2 on the plate 1 and 5 on plate 4 are arranged so as to be diagonal to each 4 other when the plates 1 and 4 are assembled and registered to make the screen, and-preferably cross each other at right angles. The

plates land 4 are assembled with the rulings on the inner side of each and theplates are spaced apart so as topermit between the two plates a medium having a different refractive effect from the two glass plates.

See especially Fig. 3, by'way of illustration.

In this figure, the features to which reference characters 2, 3, 5 and 6 appertain are not visible, the reference numerals and their lead lines in this instance being used to show the locations rather than the things themselves. According to one feature of the invention said intervening medium has also a diflusial action on the light. Certainof the superior results may be obtained by having the intervening medium such thatthe action on the light is diflusive without the refractive effect ofsaid intervening medium being diiferentfrom that of the glass.

According to one feature of the invention the intervening medium used is air. The plates 1 and 2 are shown spaced apart a very little by suitable means such as strips 8 and 9, thus leaving the space 7 therebetween. By referring to Fig. 4 it will be seen that by transmitted light, the intersections of the rulings 2 and 5 present portions of stilliless translucency than the rulings themselves. The effect of the medium intervening between the two parts of the rulings cannot beshown in the drawings, but evidences itself in the plate obtained by use;

of the screen. By reason 0 tion of such medium between one set of miings'ar-l the other, it will be understood that the light action is correspondingly changed,

the intervene resulting in the closing up or connecting of the dots in the high lights with much less exposure than with the screens now in use, and thereby the middle tones are not sacrificed by being over-exposed as they always are in the connecting of the dots in the high lights when the screens now in use are employed.

In Figs. 5 to 8 the invention is shown applied also to a screen in which the rulings are partly translucent, but are parallel to each other, instead of crossing each other. In this case the plate 11 is shown withlhe rulings 12 thereon andthe highiy translucent parts 13 therebetween. On the plate 14. are placed similar parallel rulings 15 with similar spaces 16 therebetween. The rulings l2 and 15 are so placed on their respective plates that when said plates are assembled saidrulings will overlap each other in part, whereby a ruling is obtained having a central part 30 of least translucency and at either side a part of greater translucency and between these parts of still greater translucency. The members 18 and 19 are shown spacing apart the plates 11 and 14 and providing the space 17 between the two parts of the combined ruling for the intervening medium. The effect so far as the superimpositionof the rulings is concerned is shown in Fig. 8, but in this case also the effect of said intervening medium cannot be shown in the drawings.

In accordance with one feature oflhc invention, the tintings or rulings may be created by covering the surface of the plate or plates with a highly transparent or translucent emulsion, carrying a pigment of a proper shade or intensity to give the proper degree of translucency or light transmitting power or powers. Various analin dyes will be found suitable for this purpose. The plates may then be placed in the ruling machine and the coating removed and the absolutely clear glass left to constitute the parts of greatest light transmitting power.

It will be understood that the drawings represent the rulings greatly enlarged and that the drawings are in many respects necessarily more or less diagrammatic in character, but they will enable those skilled in the art to understand the invention in connection with the description.

What I do claim as my invention and desire to secure by Letters Patent,- is:

1. A half tone screen including in combination two plates of transparent material, arranged parallel to each other, but spaced a little apartso as to have a layer of air therebetween, said plates carrying a half tone ruling.

2. A half tone screen including in combination two plates of transparent material, arranged parallel to each other, but spaced a little apart,

a little apart so as to have a layer of air therebetween, each plate carrying upon its inner surface a ruling.

3. A half tone screen including in combination two plates of transparent material, arranged parallel to each other, but spaced a little apart, so as to have a layer of air therebetween, each plate carrying upon its inner surface a translucent ruling.

4. A half tone screen including in combination two plates of transparent material, arranged parallelto each other, but spaced so as to have a layer of air therebetween, each of said plates carrying a ruling, the ruling on one plate being partly in line with the ruling on the other plate in a direction perpendicular to the surface of said plates.

5. A half tone screen including in combination two'plates of transparent material, arranged parallel to each other, but spaced so as to have a layer of air plate carrying upon its inner surface a translucent ruling, the ruling on one plate being partly in line with the ruling on the other late in a direction perpendicular to the sur aces of said plates.

(3. A half tone screen including in combination two plates of transparent material, each of said plates carrying a ruling, and a gaseous substance interposed between said plates having a slight diffusing or dispersing action on the light transmitted through said screen.

In testimony whereof, I have signed my name to this specification, in the presence of two subscribing witnesses.

JOSEPH ARTHUR HENRY HATT.

a little apart therebetween, each Witnesses:

-JOHN D. MORGAN,

Rosa MENK. 

